T-K modified the cylinder on a .45 Colt Mountain Gun to accept moon-clipped .45 ACPs for me. The .45 was and remains extremely accurate with .45 Colt ammo. .45 ACP ammo does not quite perform on a level with the longer cartridge as far as pure accuracy is concerned, but I by no means consider it inaccurate......My timer tells me that in my hands, this T-K-modified Mountain Gun loads more quickly than my 5" Model of 1989 with chamfered chambers. The Mountain Gun has become my favorite firearm for use in my club's Sgt. York Category, which requires a loaded revolver and three additional loaded moon clips per stage.